Digestive System

1
Digestive System

• -disassemble food you eat so that the molecules
  can be used for energy.
• -food must not only be absorbed, but also finally
  eliminated
• -when food first enters your mouth, through the
  process of ingestion, mechanical and chemical
  digestion begin.

2
Mouth

• Tongue moves food around and positions it between
  your teeth.
• Chewing is a form of mechanical digestion
  (breaking down food)
• Chemical digestion is the process of changing
  food on a molecular level through the action of
  enzymes.
• Chemical dig. Begins in the mouth.
• Your saliva contains an enzyme called amylase,
  which breaks down starch into smaller molecules
  such as mono or disaccharides. Amylase continues
  to work in the stomach for about 30 mins.

3
Esophagus

• After chewing, your tongue shapes your food into
  a ball and move it to the back of your mouth to
  be swallowed.
• As you swallow, a cartilage flap (epiglottis)
  covers your trachea (windpipe) so that you dont
  choke. down the wrong pipe.
• Swallowing forces food into your esophagus a
  muscular tube that connects your mouth to your
  stomach.
• Food moves down the esophagus by means of
  peristalsis a series of involuntary smooth
  muscle contractions.

4
Stomach

• After swallowing, food enters the stomach
• It is a muscular, pouchlike structure
• Both mechanical and chemical digestion take place
  here
• Mechanical- actually muscles churn food.
• Chemical the stomach secretes gastric juices
  containing pepsin (works on proteins) and HCl
  (provides an acidic env. Which pepsin likes).
• pH about 2 (a thick mucus lining protects it form
  the acid)
• Food remains there about 3-4 hrs.

5
Small intestine

• When food is ready to leave the stomach, it has
  the consistency of tomato soup. Peristaltic
  waves begin to push it into the SI, which is
  about 6 meters long and has 3 distinct parts.
• Digestion of your meal is completed here.
• Muscular contractions continue to break down
  food.
• Carbs and proteins are broken down with the help
  of enzymes produced by the liver and pancreas.
• These enzymes from the liver, pancreas and gall
  bladder enter the SI through ducts.
• These organs are important even though food does
  not pass through them.

6
Pancreas

• Secretes both digestive enzymes and hormones
• The enzymes it secretes breaks down carbs,
  proteins and fats.
• It also helps to neutralize the acidity of the
  liquid food, stopping any further action of pepsin

7
Liver

• Very large, complex organ with many fxns.
• Produces bile (breaks down fats)
• Bile is stored in the gall bladder.

8
Absorption of Food

• Liquid stays in your SI for 3-5 hrs. and is moved
  slowly via peristalsis
• As it moves it passes by 1000s of tiny fingerlike
  projections called villi (they greatly increase
  surface area)
• Villi absorb digested food molecules which then
  diffuse into tiny blood vessels of the villus and
  enter the bloodstream.
• The villi are the link between the digestive
  system and the circulatory system.

9
The Large Intestine

• Indigestible material form your meal now passes
  into your LI, a muscular tube that is also called
  the colon. It is much shorter than the SI, but
  it has a larger diameter.
• The LI is greatly responsible for water and salt
  absorption, leaving behind solid waste.
• It is also resp. for vit. synthesis. Anaerobic
  bacteria in the LI synthesize some B vits. And
  vit. K, which are absorbed as needed by the body.